Considerable expense is involved in the construction of an elevator hoistway and machine room. The expense includes the cost of constructing the machine room, the structure required to support the weight of the machine room and elevator equipment, and the cost of shading adjacent properties from sunlight (e.g., sunshine laws in Japan and elsewhere). The expense also includes the length of the hoistway. Typically, local codes require a minimum clearance between the top of the elevator car at its highest position in the hoistway and the hoistway ceiling. Conventionally, the highest item on top of the elevator car is the door operator which is located on top of or projects partly above the elevator car ceiling. By eliminating or minimizing the highest points on top of the elevator car, the length of the hoistway may be reduced so as to result in a significant reduction in construction costs.
One solution is to move the door operator underneath the elevator car. However, this approach only results in shifting the clearance problem since additional space is required in the lower portion of the hoistway to accommodate the door operator. Another solution is to move the door operator to a side of the elevator car. A drawback with placing the door system on a side of the car is that additional space between the car and hoistway sidewall is necessary to accommodate rather bulky, conventional motors which drive the elevator car and hoistway doors. Thus the additional side space required to accommodate the drive system detracts from any savings due to reducing the overhead space of the hoistway.
It is an object of the present invention to provide an elevator door system which avoids the above-mentioned drawbacks associated with prior elevator door systems.